export default (req, res) => {
  /** setPreviewData设置的值必须是一个对象，且他必须能被getStaticProps使用*/
  res.setPreviewData({
    a:'a'
    ,b:'b'
    ,xxx:'yyy'
  });

  /** 关于数据能传递的大小限制
   However, because the data will be stored in a cookie, there’s a size limitation. Currently, preview data is limited to 2KB.
   */
  res.end('Preview mode enabled');
}

